Low-stress tantalum absorbers deposited by sputtering for x-ray masks

Abstract

A method for fabricating stable and low-stress tantalum films, suitable for absorbers of x-ray masks, by dc-bias, rf magnetron sputtering is presented. The superiority of Xe over Ar as a working gas is demonstrated. The stress-vs-bias-voltage curve has a plateau, where the film stresses are low and constant over the bias voltage ranging from −15 to 20 V. The plateau stresses vary linearly with both the working Xe pressure and the substrate temperature with slopes of 1.2×1010 dyn/cm2 Pa and 8.6×106 dyn/cm2 deg, respectively. By control of the pressure and the temperature, stresses of (3±2)×108 dyn/cm2 are achieved. The Ta film which is stable under a heat treatment up to 300 °C is obtainable when it is deposited at 220 °C and then annealed at 220 °C for 1 h. The density of the films is (15.0±0.5) g/cm3. By x-ray diffraction the films are found to be in a mixture of the α-Ta phase and the β-Ta phase. Ta patterns of 0.15 μm in width were fabricated.

Stress Reduction of Ge<SUB>2</SUB>Sb<SUB>2</SUB>Te<SUB>5</SUB> by Inhibiting Oxygen Diffusion

“…According to a report, the stress-change in air is much larger than that in nitrogen, 13) which has been explained by oxygen diffusion into Ta film. [13][14][15] The stresschange is increased with annealing temperature and time, and is directly proportional to the diffused oxygen content in Ta film. 13) Additionally, the large distance of oxygen diffusion into Ta film is understood to be due to the high diffusion rate of oxygen along the grain boundaries of the Ta.…”

Masks for high aspect ratio x-ray lithography

“…Tungsten [32][33][34][35][36] or tantalum [37] films with low stress values require a fine control of the deposition parameters. Such films are intrinsically thermally more stable than gold, due to the refractory nature of these elements, but stress evolution can also occur depending on the microstructure of the film.…”

Effect of various sputtering parameters on Ta phase formation using an I-Optimal experimental design

“…Tantalum thin films are used in a variety of applications. For example, Ta can be used as a diffusion barrier between Cu and Si [1], a gate electrode in MOSFET's [2], and as an x-ray absorber in x-ray masks [3] [4] [5] [6] [7] [8]. Further, Ta is often used as a protective overcoat above the resistor in inkjet devices.…”